Quality of Service (QoS) broadly refers to a network's ability to provide better service to selected network traffic. QoS can be characterized by several basic performance criteria, including availability, error performance, response time, lost traffic or poor transmission due to network congestion, and so on.
While QoS for networks is a fairly developed field, network storage systems pose special problems which are not addressed by prior art QoS protocols and techniques. As an example, in an Internet Protocol (IP) network, most of the heavy traffic is from the server to the client. Typically, the traffic may be in the form of downloads from the server to the client. Accordingly, prior art QoS techniques are designed to address unidirectional traffic from server to client.
However, in network storage, heavy traffic may be bi-directional, such as either a read activity or a write activity. Read activities may create heavy traffic from the storage server to the client. In contrast, write activities may create heavy traffic from the client to the storage server. Prior art QoS techniques are not equipped to address bidirectional traffic.
Another network storage issue is non-compliant clients. In IP network traffic, most of the traffic from the client is negligible in comparison to the traffic from the server. Consequently, damage caused by clients that are non-compliant with service level agreements is typically inconsequential. Thus, prior art QoS techniques do not address the issue of non-compliant clients. In contrast, in network storage systems, a non-compliant client may initiate a number of heavy traffic activities, such as read or write of data. In QoS for network storage, there is therefore a need to track and contain traffic of non-compliant clients. This need is currently not met by prior art QoS techniques.
The above are just two examples of the inability of prior art QoS techniques to address QoS issues for network storage systems. There is therefore need to provide QoS techniques that can address the unique and specific issues of network storage systems.